From 5da7667c035f3a711ec8d0a3997254807dd8bc6d Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky <schwidefsky@de.ibm.com> Date: Mon, 28 Sep 2015 15:27:26 +0200 Subject: [PATCH] s390/barrier: remove unnecessary serialization in atomics and bitops The principles of operation states reads are in order, writes are in order, writes can be reordered after reads, but no reads can be reordered after writes. The atomic and bitops variantes for z196 use the interlocked-access facility instructions with a memory barrier before and after the instruction. Because of the memory ordering the first barrier is unnecessary and can be removed. Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> --- arch/s390/include/asm/atomic.h | 2 -- arch/s390/include/asm/bitops.h | 1 - 2 files changed, 3 deletions(-) diff --git a/arch/s390/include/asm/atomic.h b/arch/s390/include/asm/atomic.h index 117fa5c921c1b..911064aa59b2f 100644 --- a/arch/s390/include/asm/atomic.h +++ b/arch/s390/include/asm/atomic.h @@ -36,7 +36,6 @@ \ typecheck(atomic_t *, ptr); \ asm volatile( \ - __barrier \ op_string " %0,%2,%1\n" \ __barrier \ : "=d" (old_val), "+Q" ((ptr)->counter) \ @@ -180,7 +179,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u) \ typecheck(atomic64_t *, ptr); \ asm volatile( \ - __barrier \ op_string " %0,%2,%1\n" \ __barrier \ : "=d" (old_val), "+Q" ((ptr)->counter) \ diff --git a/arch/s390/include/asm/bitops.h b/arch/s390/include/asm/bitops.h index 66a1cff673531..47bd0878a0067 100644 --- a/arch/s390/include/asm/bitops.h +++ b/arch/s390/include/asm/bitops.h @@ -64,7 +64,6 @@ \ typecheck(unsigned long *, (__addr)); \ asm volatile( \ - __barrier \ __op_string " %0,%2,%1\n" \ __barrier \ : "=d" (__old), "+Q" (*(__addr)) \